- Features of a long burning fireplace
- Operating principle
- Long burning fireplaces
- Long burning fireplace stoves
- Fireplace inserts
The modern classic closed-type wood-burning fireplace differs from the stereotypical one familiar from movies and books. Thanks to new technologies, this is a full-fledged heating device with high efficiency and a decent power level, sufficient to heat a summer cottage or a small house.
Features of a long burning fireplace
A classic wood-burning fireplace with an open hearth can be used either as a decorative element of the interior, or as a way of relaxation. Its use as the main heating device, given the level of efficiency up to 20%, is unprofitable even for small rooms..
An open firebox and, as a result, a constant flow of a large volume of fresh air lead to a high burning rate and incomplete combustion of fuel.
The first factor is the reason that the bulk of the heat simply “flies out into the pipe” along with the combustion products.
In the second case, we can talk about several negative components at once:
- incomplete burning of firewood and a large percentage of solid residues;
- high content of solid fine fuel particles in flue gases;
- incompletely burnt carbon in the form of carbon monoxide CO;
- incomplete combustion of pyrolysis gases.
To understand the significance of the afterburning of pyrolysis gases, suffice it to say that in addition to carbon (the solid residue is charcoal), firewood also contains other combustible substances that wood releases when heated. The most famous volatile fraction is methyl alcohol (aka wood), and there is also acetone, benzene and others. By the way, it is the combustion of pyrolysis products (and not carbon) that gives such familiar tongues of flame (be it firewood, coal or liquid fuel).
The design of long-burning pyrolysis furnaces with a closed firebox allows almost completely burning all combustible substances in solid fuel (in this case, wood or pellets).
The fundamental difference between a long-burning fireplace and a classic model is a closed firebox and a lack of oxygen.
In fact, there is no burning of wood, but their smoldering in the lower part of the furnace, as a result of which a large amount of flammable gases are released. Most of the heat is obtained during the afterburning of these gases in the upper part of the furnace. Therefore, the air is supplied separately: to the lower part (primary air) and the upper part of the furnace (secondary air). It is the “two-stage” burning of wood that gives the maximum effect.
According to the principle of operation, long-burning fireplaces do not differ from gas-generating (pyrolysis) solid fuel boilers and stoves. Thanks to this, their efficiency can reach 85% (for models with one reflective surface).
Visually, the difference between fireplaces and boilers and stoves is that they have a large door made of heat-resistant glass (decorative functions must be present). In addition, they have an “incomplete” principle of laying firewood in the firebox (if we compare the same volumes), so the burning time of one bookmark in fireplaces is less.
The fundamental difference is in the method of heat transfer. For boilers, piping and transportation of the coolant is needed, and convection (convective) ovens use a system of pipes surrounding the firebox, from which heated air enters the room. Long burning fireplace gives off most of the heat by radiation (radiation).
A closed firebox restricts air access to the upper and lower parts of the combustion chamber, and in order to see the fire in the fireplace, the glass door must remain clean and transparent. This is achieved with the help of secondary air – its supply is arranged in such a way that the inner surface of the door is blown, and soot does not settle on the glass.
It is practically impossible to achieve such “abilities” in a fireplace made by hand from fireclay bricks – too complex gas-dynamic processes must be taken into account in a structure that has a pronounced “individuality”. Therefore, we can only talk about devices with a high degree of factory readiness..
Long burning fireplaces
By the type of construction, two large classes can be distinguished:
- fireplace stoves;
- ready-made fireplace inserts.
Long burning fireplace stoves
These are ready-to-install heating devices that do not require installation and decorative finishes..
They are distinguished from ordinary wood-burning stoves by their rather large glass doors. All that needs to be done is to bring a chimney of the appropriate diameter (often the manufacturer indicates the recommended type) and protect the adjacent surfaces.
The fireplace stove does not require cladding – its body can be made of cast iron with artistic casting or steel coated with heat-resistant ceramics (for example, majolica).
Small dimensions and relatively low weight do not require reinforcement of the floor slab or the construction of a separate foundation. But this also imposes restrictions on the thermal power – usually the model range of most manufacturers has a range from 4 to 10 kW. And if we consider that for heating a room of standard height (2.5-3 meters), a ratio of 1 kW per 10 square meters is taken. m, then this is the best choice for small cottages and country houses.
There is another significant advantage of fireplace stoves – most models have hobs, and some are also equipped with ovens.
There are products of higher power (from 15 kW) that can heat an area up to 200 sq. m.But in this case, you can already go to the next class and choose long-burning fireplaces based on the finished firebox.
These are more powerful heating devices, the range of which starts from 10 kW.
On their basis, you can equip a fireplace that can heat a house from 100 to 250 sq. m. And if the fireplace is connected to a hot air distribution system (air heating), then it is able to heat several rooms in one or two levels.
Depending on the type of firebox, you can make any type of fireplace: built-in, wall-mounted, corner (with one or two panes), island (with three panes).
Its cladding can be made from a ready-made fireplace set, choosing materials and design for a specific interior style. But the portal can be made according to an individual project..
The cladding, the weight of the furnace and the chimney exert a significant load on the ceiling, therefore, reinforcement of the base or even a separate foundation is often required.
Both fireplace stoves and ready-made fireplace inserts are made of metal, but high temperatures and the effects of combustion products destroy it.
The most durable is cast iron (as well as for heating boilers).
Steel furnaces and fireplaces are prone to deformation and burnout, so they have a lining – a protective inner lining made of heat-resistant material. This is either cast iron or special ceramics..